Systematic investigation and understanding of small particles and biological cells depends on the tools available with which to probe particle or cell function. An important aspect of cell function is the interaction between two cells. Such interaction occurs at the interface and requires close contact between the two cells. Interaction between cells involves signaling, exchange of membrane material, exchange of intracellular material and fusion of the cells. For particles other than cells, interfacial interaction can result in chemical bonding of two particles and in chemical reactions between two particles. Currently, an ability to capture and pair particles in isolated, defined positions and with high yield is lacking.
The main methods for particle/cell capturing and pairing involve the manipulation of one pair at a time. Usually, one particle/cell is held by one syringe/pipette, and is brought into contact with another cell held at the tip of a second syringe under a microscope. Alternately, one cell can be immobilized on a surface and the other cell will be brought into contact with it using a syringe. Optical trapping of one cell/particle in solution enables the controlled transfer of such cell into contact with another cell that is held by a syringe, an immobilizing surface or an additional optical tweezers. Another method relies on the growth of two neighboring cells until they reach each other and become contacted on a surface.
Large populations of cells/particles can be mixed in solution and get into contact. Solution conditions such as concentration and temperature can enhance such interfacial contact between cells. Chemical functions on cell membranes and on particle surface can cause the binding of cells in solution. However, such binding/contact might be temporary, is not selective, the location of the pairs is not defined and the pairs are not isolated for further analysis.
A device and methods are needed for the specific capturing and pairing of two cells/particles, in predetermined positions, such that the two particles forming a pair are isolated from other pairs, immobilized, their surfaces are in close contact and the identity of each particle is controlled. A device and methods are needed for the observation and manipulation of such pairs. A device and methods are needed for high yield reactions between particle/cell pairs and for the controlled release and collection of the final product or modified cells.